This invention relates to an adaptive data compression method and the corresponding encoder and decoder.
The expression "data compression" here means a means of replacing a digital message by as short a message as possible from which the initial message can be retrieved exactly. The operation of transformation of the original message is called source encoding, in the information theory sense, and the opposite transformation which retrieves this message is called decoding.
The method is adaptive in that it does not require any prior statistical knowledge of the source of the message to be coded. In fact, there are numerous practical situations in which this knowledge is partial or even absent. For instance, a data file does not usually correspond to any statistical structure known a priori.
The method embodying the invention is of the type described by GUAZZO in the article entitled "A General Minimum-Redundancy Source-Coding Algorithm" published in the IEEE Transactions on Information Theory, volume IT-26, number Jan. 1, 1980, pages 15 to 25, for a source of which the probabilities are known and stationary.